From an anonymous maleDear Carole, A close friend has recently become engaged to her boyfriend. We, her friends, are unanimous in our disapproval. We have never liked her boyfriend, but have maintained a tactful silence; we felt things would come to a natural end without our interference.

It seems we were wrong.

He is not an attractive man, he is not particularly successful, not rich, not exotic and interesting, not creative, not charming. He has an active, if rather crude, sense of humour, which I accept she may appreciate more than we do, but he is sleazy, and acts inappropriately towards her female friends.

She, on the other hand, is attractive, intelligent, independent, and a thoroughly sunny person, but she has a serious lack of experience with relationships. In the many years we knew her before her current relationship she was always single, going on first and sometimes second dates, but never starting relationships or flings. She may associate the benefits of being in a relationship with this man, not realising that the same benefits would come from any relationship.

He is pushy, and self-confident, and I'm sure it is these attributes that got him into the relationship in the first place. He courted her with a cringe-worthy forthrightness. She hates to cause people offence and, it seems, is incapable of saying no.

We need to stop this. We need her to ditch the unworthy mate.

If we fail and she goes through with the wedding, I will of course support her. I will never mention her partner's inadequacies, I will help her cope with her inevitable regret, and I will strongly encourage her to sleep with her personal trainer for the sake of her children's genes. But before I have to take my seat in the church and forever hold my peace, what can I do?

Ask Carole: Chimpanzee wearing spectacles Photograph: Public Domain

Carole replies:Natural selection is not a process that always offers happy endings. Rather, it is the mechanism by which the fittest survive. Golden wedding anniversaries have not been selected for – sometimes the sexual attraction between couples only lasts long enough for a child to be conceived.

You say he has little to offer in terms of creativity, charm or attractiveness, yet, nonetheless, he is confident with a pushy cringe-worthiness – it sounds as though he lacks self-awareness. She, on the other hand is described as being intelligent, sunny and incapable of saying "no" for fear of hurting others – it sounds as though she may suffer from runaway empathy.

If she is highly self-aware her pathology may compel her to accommodate his lack of the same. Sexual attraction is a complex phenomenon. People often seek out significant others who exhibit traits they themselves lack.1 Indeed, if these two people are opposites, this may add to the mutual attraction.2

A child born from this relationship might inherit a sunny, intelligent, attractive, self-confident pushiness. All good qualities when it comes to reproductive fitness. On the other hand the child could inherit a sleazy lack of charm and an inability to say no – not such a good combination. In spite of the meteoric advances in the science of genetics, primate inheritance is complex and remains highly unpredictable. Add to that the impact of the environment on children, where one wrong move can have a knock-on effect that negatively affects the long-term success of a promising individual, and it's clear that predicting individual outcomes is nigh on impossible.

This couple could produce a wonderful new infant who will grow to achieve greatness. Any problems they experience may stem from their differences, which ironically may be part of their initial sexual attraction. But the evolutionary cause of producing fit offspring will have been served.

As for happiness, if 10 years from now your friend has some kind of crisis, but her partner's lack of self-awareness means he cannot provide the neccesary emotional support, she will need you and her other friends more than ever. I can only hope that the inappropriate sleaziness of this man won't have driven away her friends before their first wedding anniversary.

If you feel as strongly as you say you do and you are a "close friend" to this woman then why have you remained silent? Shouldn't you be saying to her what you have said to me?3 Do you fear ostracism from your clique and exclusion from the wedding if you speak out? If you genuinely care about this woman you should place your feelings of concern for her above your own fears of social isolation.

It is an understandable weakness to remain silent for fear of hurting the feelings of others and perhaps being cast out. Messengers do get shot from time to time (and an ostracised primate's survival chances are much diminished4). But this same inability to say "no" is something you accuse your female friend of. In fact you cite it as a cause for her present predicament.

You need to find the courage to stand up for what you believe in and learn to say what's on your mind, just as much as your friend needs to hear it to learn the same lesson and say "no" to this man.